1. Field of the Invention
This invention relates to flow control surfaces with retractable vortex generators.
2. Description of Related Art
Vortex generators have been used with a variety of flow control surfaces to mix low momentum fluid flow associated with a boundary air layer of the flow control surface with a high momentum fluid flow outside of the boundary air layer. The use of such vortex generators in a variety of aircraft have produced improvements in maneuver effectiveness. However, permanently installed wing vortex generators produce drag penalties and may accrete foreign matter such as ice shapes that significantly degrade the proper performance of the aircraft.
Retractable vortex generators have been developed to compensate for these problems.
Bauer U.S. Pat. No. 4,039,161, Cox U.S. Pat. No. 5,253,828, and Lisy et al. U.S. Pat. No. 6,105,904 each disclose vortex generators which may be retracted into a flow control surface. However, the retractable vortex generators described in these documents require modification of the structure on which it is disposed to allow for internal space into which the vortex generator may be retracted when not in use. This requirement for adequate space to accommodate the vortex generators may influence the design of the wing or other structure in a negative manner. This also requires that a wing, or other such structure having a flow control surface to which a vortex generator is desired to be added cannot be easily retrofitted for such vortex generators.
Campbell U.S. Pat. No. 6,427,948, discloses a vortex generator which is capable of being selectively moved into a deflected position to produce downstream turbulence and moved into an undeflected position to reduce drag. The vortex generator of Campbell is formed of a shape memory alloy that is in the deflected position when no electric signal is applied to an associated heater and is in the undeflected position when an electric signal is applied to the associated heater. However in both the deflected and undeflected states the vortex generator protrudes outside of the flow control surface and, while the undeflected state may produce less drag in comparison with the deflected state, the protrusion will still produce some undesirable residual drag and does not alleviate the problem of ice accretion on the exposed vortex generators.